Residents Association - What is it?

Hello,

Am very excited at having just put in an offer on a beautiful flat at the top of the building.
The estate agent told me and my boyfriend that the building is mutually owned by the residents and the forum for any decisions being made is the residents association. The service charge goes into a pot for any maintenance work in the building. On first glance this seems a real draw, but I have a few questions itwould be great is people could answer.
Who is there a chair of the residents association?
What was the process of decision making for the mobile phone masts being placed on the top of the building?
The service change is quite alot higher than other places. (I live in a high rise at the moment down the road in Hackney. The service charge is much less, but we get 24 hour concierge and a gymn. What is the reason for it being so high?
Any other relevant information you could give me would be great.

Thankyou.